Psychology / Circadian Rhythms

Circadian Rhythms

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Autor:  anton  08 September 2010
Tags:  Circadian,  Rhythms
Words: 2487   |   Pages: 10
Views: 272

Tomas Izquierdo has not slept since 1945. Due to an attack of encephalitis, an inner brain inflammation, his ability to fall asleep was lost at the age of 13. Although he rests with his eyes closed, his brain patterns are those of someone who is fully awake and aware. He has memory problems and very sensitive eyes, but is otherwise completely normal. To relax, he usually uses transcendental meditation from about three or four AM until the morning (Coleman 94).

Tomas Izquierdo is what one might call someone without circadian rhythms. Circadian rhythms are the daily sleep patterns of humans. Circadian rhythms tell people when they are most alert, when they feel tired, and when they should wake up. These circadian rhythms, while difficult to research, are important to many industries, as well as a multitude of sleep disorder patients. For several years, scientists and doctors have been seeking a greater understanding of these patterns through constant, difficult, and fast paced research. The applications of such knowledge would be quite beneficial in shift based industries as well as some special circumstances. As of yet, doctors have been able to determine a few important correlations between internal time cues and sleep, activities or events that give cues to the brain about what time it is or should be. However, the research is very difficult.

Researching sleep is difficult for a variety of reasons. The first reason for difficulty is the nature of experimentation. To truly isolate the sleep patterns, all time-giving cues, or zietgebers, have to be eliminated. Light, electromagnetic waves, the schedules of researchers, and even the growth of a facial hair on outsiders may lead the subject to guess the time of day. The body can detect even the faintest cues of time, so it is incredibly important that the subject be completely shut off from time giving cues. If the subject of the research knows the time of day, he or she may adjust accordingly, skewing results and making it all but impossible to collect the data needed.

Another reason for the difficulty of sleep research is the pace of discovery. The field moves too fast for its own good. As a result, no comprehensive beginner’s text is available in the field of circadian rhythms. By the time a book would go to print, too much important experimental evidence would have been released for it to be considered up to date. So, as of yet, most research in circadian rhythms remains in the form of scientific newsletters and magazine articles. While this is a good way for those who are up to date in the field to stay current, it is all but impossible for an outsider to understand. Due to this lack of an introductory text, doctors have a more difficult time learning what has already been proven about sleep (Simon Frasier).

A third difficulty in researching circadian rhythms is the lack of test subjects. While being paid for sleeping may sound enticing, the reality of research is much different. People are cut off from contact with their families and loved ones for months and put in what amounts to a jail cell. The room is easily compared to the small boxes used by psychologist B.F. Skinner to test theories of conditioning on mice; not exactly the nicest of conditions to live in. Subjects are allowed to read old magazines and newspapers, but no current information is available. If a war were to break out, the subject wouldn’t know about it until after the study was completed. Live feed-type entertainment such as radio or television is not allowed. In addition to a lack of freedom and information, the subjects are tested quite often. For example, take the case of one such study at the Laboratory of Human Chronophysiology at Montefiore Hospital. In the study, subjects had small blood samples taken every twenty minutes, alertness tests about every hour, brainwave monitoring of any sleep, and continuous rectal temperature readings (Coleman 7). Subjects of any such research have to be crazy enough to willingly go through this kind of testing but sane enough to call normal. The experience was described by Preston Keogh, a subject, in his journal.

“Sometimes I felt like a prisoner, trading my youth for money. Although I didn’t feel crazy, I thought others might think I was… They took blood samples every fifteen minutes. I had a catheter in my arm, and a butt probe and all these things were attached to a movable pole. The first few days there was a definite presence but after the first week it became a part of you. It was like having a tail.”

Finding people who are willing to live in these conditions is a major obstacle to research.

It could be asked, “If it’s so hard to do, why bother with all this research? What’s so important about sleep patterns?” The importance of sleep pattern research is threefold. Not only will research in the field of circadian rhythms help us maximize the alert hours of the general population, but it will also help to better maximize the schedules of shiftworkers. Shiftworkers are laborers, usually factory based, that run on a continuous 24 hour schedule, never stopping. The idea of shiftwork is that expensive or crucial machinery can be kept operating 24 hours a day. For example, a telephone operator or a nurse would work on a 24 hour shift system. Sleep pattern research with also help set the schedules of people in situations where the time-giving cues of light are not available, such as in spacecraft or submarines. To be able to get shiftworkers or submarine crews to work more efficiently might mean that less people and equipment may be needed, possibly saving hundred of thousands of dollars. The first step in this research is defining a normal sleep pattern.

Research has defined a “normal” sleep pattern for adults. Studies have been done all over the world in the field to describe what is considered normal among adults. In one such study sponsored by Stanford University, three rooms of a hospital were sectioned off for testing. The center room was used as a control room, and the other two rooms were used as bedrooms for test subjects. The test subjects were instructed to stay in the rooms, which had no windows or clocks, and sleep on a regimented schedule for twenty days. After the twenty days passed, they were told to sleep whenever they wanted to. The scientists asked that they take only one sleep period a day. Volunteers had no contact with the outside world other than the staff. The staff, of course, was instructed to remove any trace of a sense of time from their habits. They had to remove all wristwatches, use time-neutral phrases like “hello” instead of “good morning,” and shave just before handling test subjects. Their work schedules were determined randomly by computer. Even with all of these precautions, the test subjects mostly followed identical patterns of sleep. These somewhat identical sleep patterns were therefore dubbed “normal” and taken as natural (Coleman 6).

Normal sleep patterns include a few main ideas. First, most adults sleep for about eight hours each day. If asked to sleep less, most can function at the same level of efficiency with less sleep. In fact, after eight weeks of sleeping for five and a half hours a night, most subjects report that they no longer felt drowsy during the day. However, these sleep deprivation studies have shown that even after months of sleeping four or five hours a night, people go back to the eight hour standard citing that they just feel better when they get more sleep (Coleman 98).

In addition to an eight hour sleep period, normal sleep patterns include free running. Free running is the practice of going to sleep one hour later than the night before. In the aforementioned Stanford study, most subjects were found to fall asleep an hour after they would have the night before. Scientists believe that this phenomenon, called free running, is due to a natural 25 hour cycle that humans run on. In the absence

of time cues, 25 hours seems to be the preferred length of day for the average adult (Coleman 8).

Beyond the 25 hour cycle, scientists know bits and pieces of other information. For example, scientists know a small amount about alertness levels. Alertness levels are highest during the middle of the day, and lowest during the first hour before and after sleep. After a sleepless night, a normal person will return to higher alertness on the cue of light. So, if a person were to stay up all night intentionally, they would feel somewhat refreshed in the morning, even without sleep. This feeling, of course, lessens over repetition, so sleep cannot be abandoned altogether. Now that scientists know some of the basics of normal sleep patterns, the next step in research is correlating between time cues and those sleep patterns (Coleman 20).

Currently, research shows several correlations between certain time cues and circadian rhythms. One such time cue is light. For example, people in subarctic climates often have very long or very short days. During winter it can stay dark for all 24 hours of the day. As a result, some people suffer from SAD, or Seasonal Affective Disorder. Those with SAD have symptoms of depression, increased weight, and, perhaps most importantly, sleepiness. According to Richard Coleman, the disorder is related to the secretion of melatonin, a hormone that is released from the pineal gland during the night. The body senses that it is dark, and then responds by secreting melatonin. Those with the disorder actually suffer from an overdose of melatonin due to the lack of daylight. By not getting enough sunlight, their bodies over-secrete melatonin, causing the symptoms above. By having the patient sit in front of a light for three to five hours, doctors have reduced the amount of depression and sleepiness in many cases by simulating a 13 hour light cycle. This 13 hour light cycle is very similar to the light cycle of those found in warmer climates, and is much more beneficial to those with SAD.

It may seem odd that the body could unconsciously identify the availability of light, deciding when to be alert and when not to be based on the presence of light or lack thereof. However, such light-sensing can be physiologically explained. Last April, Dutch and Japanese scientists studied mice without normal rods and cones in their eyes. Rods and cones are the light and color sensing structures of the retina that allow animals the sense of vision. Their research indicated that the mice could still reset their circadian clocks, even without the help of these light sensing structures. So, in effect, the blind mice could tell when there was light and when there wasn’t. Their conclusion was that there had to be another structure within the eye that senses light for the purpose of circadian rhythm regulation. The importance of this conclusion is that if scientists could isolate and study the structure, then they could better diagnose and treat SAD as well as a variety of sleep disorders (Circadian).

Another physiological reason for the regulation of circadian rhythms is the presence of Cryptochrome, or CRY, an eye pigment protein found in mammals. In a study at the University of North Carolina, two individual types of CRY were found to cause changes in the speed of the biological clock. They were named CRY 1 and CRY 2. (Discovery). In mice, CRY 1 deficiencies sped up the biological clock, while CRY 2 deficiencies slowed it down. (Circadian) So, in effect, scientists have located the tools to adjust the circadian rhythms of just about any mammal. However, the location of the tools is not important unless they can be used.

Geneticists working on the human genome project have already located and identified the genes responsible for the production of the pigments. The human genome project is the project to map an entire DNA strand systematically and know what each part of the strand does. Using this gene technology, scientists have spliced the DNA of humans together with that of bacteria to produce artificial bodily substances like insulin. This artificial insulin is the same as human insulin in every way, except for the fact that it was made by bacteria. Scientists may some day be able to use their knowledge of these CRY pigment genes to produce an artificial supplement, somewhat akin to artificial insulin. Such a drug would provide a more natural way of regulating the sleep cycles of narcoleptics, insomniacs, and many other sleep disorder patients.

Another important correlation that scientists have found is age. The elderly are often the most restless of all the people in our society, taking less hours of sleep than anyone else. 40% of all sleeping medications are prescribed for the elderly. As humans age, a part of their brain known as the suprachiasmatic nucleus, or SCN, gets smaller. The SCN is the primary pacemaker for most circadian functions in the brain. It is responsible for the production of the sleep hormone melatonin. As the SCN decreases in size, less melatonin is produced, causing a shift in sleep patterns. The drop in melatonin, just as in SAD patients, can cause restlessness. In order to counteract this melatonin loss, many of the elderly sit in front of light boxes, just like the SAD patients, at the end of the day for a few hours (Center for Biological).

Circadian rhythms are part of the daily lives of humans. They cue our levels of alertness, our need for sleep, and our time of waking. To better understand these rhythms, scientists from around the globe have participated in difficult research for years. As of yet, the research shows that light, hormones, exercise, age, and a variety of other factors are important in determining circadian rhythms. Perhaps in the future, scientists will be able to manipulate circadian rhythms so that people no longer feel fatigue. By then, maybe Tomas Izquierdo could finally get some long overdue sleep.



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